Meccanismi patogenetici della fase CRPC e dati
preclinici
Elisa Zanardi
UOC Clinica di Oncologia Medica Ospedale Policlinico San Martino
Dipartimento di Medicina interna e Specialità mediche (DiMI) Genova
Le origini della fase CRPC
Huggins C. Endocrine-induced regression of cancers. Cancer Res 1967
Nobel Prize Lecture
December 13, 1966 “The first series of patients with prostatic cancer treated by orchiectomy comprised 21 patients with far advanced metastases;
only 4 of them survived for more than 12 years. Despite regressions of great magnitude, it is obvious that there were many failures of
endocrine therapy to control the disease……”
Androgen Independence (AIPC)
Hormone Resistance (HRPC)
Castration Resistance (CRPC)
Teoria della fase CRPC
Isaacs JT, Coffey DS. Cancer Res 1981.
Tombal B. Eur J Cancer. 2011
ADT
Teoria adattativa Teoria della selezione clonale
Castration
resistance
CRPC:
Teoria della selezione clonale
• ADT induces selective outgrowth of aggressive hormone-refractory PCa clones expressing distinct cellular and molecular properties not present in parental androgen-dependent cancer cells
• Craft and colleagues demonstrated that the latter stage of CRPC results from clonal expansion of androgenindependent cells that are present at a frequency of about 1 per 105−106 androgen- dependent cells
• Prostate tumours are comprised of a spectrum of cells with varying androgen sensitivities even before androgen therapy is started.
• CRPC cells may originate from a long-term resident pool of PSA cells and TA cells that are insensitive to AR pathways
• NE cells are AR independent and do not induce apoptosis upon ADT. NE differentiation may contribute significantly to the development of CRPC due to its multiple drugresistance features
• Androgen-dependent PCa cells acquire mutations to become androgen-independent (PI3K, BCL-2, TMPRSS2-ETS)
Tso Cl, Cancer J 2000; Shah RB, Cancer Res 2004; Mehra R, Cancer Res 2008;
Fixemer T, Prostate 2002
CRPC: Teoria adattativa
• The major argument in favour of the “adaptation” model is
the evidence of retention of AR signaling in CRPC.
• Notably, castration resistant tumours express AR as well as AR target genes such as PSA, indicating that pathway
activity is intact
Ymamura Y and Sadar M, Int J Urol 2016
CRPC: Teoria adattativa
Most CRPC is considered to still be driven by transcriptional active AR.
CRPC: Teoria adattativa
• Amplification of AR gene copy number
occurs in approximately one-third of CRPC
• This results in a higher quantity of the wild- type AR protein and therefore in a higher sensitivity and responsiveness to low levels of circulating or intracellular androgens, causing a survival and growth advantage upon castration.
• Patients with an AR gene amplification
progressing after a first line of LHRH agonist had a 4.5 higher likelihood to respond to a subsequent maximal blockade
• An increased AR level can convert an
antiandrogen such as bicalutamide from an AR antagonist to an AR agonist, and this is one of the explanations for the well-known antiandrogen withdrawal response
Visakorpi T,. Nat Genet. 1995
CRPC: Teoria adattativa
• Several mutations have been identified that may confer increased AR protein stability, greater sensitivity to androgens, aberrant responses to antiandrogens or other steroid hormones, ligand-independent activity, or increased recruitment of AR co-activator Proteins
• AR gene mutations in the LBD may alter ligand binding, leading to AR activation by AR antagonists and other ligands that do not activate wild-type AR, another
explanation to the antiandrogen withdrawal syndrome.
• Mutated AR may lack the entire LBD, leading to an auto-activated mutant that mediates AR signaling independent of any ligands
Sun C, Shi Y, Xu LL et al. Oncogene 2006;
CRPC: Teoria adattativa
• Several co-activators, including TIF2, SRC1 and TIP60, have been shown to be overexpressed or accumulated in the nucleus of recurrent PCa specimens
• AR overexpression increases the
expression of androgen-stimulated co- activators such as MAK, BRCA1, AIB1, or CB.
Agoulnik IU, Cancer Res. 2006;
CRPC: Teoria adattativa
• IL-6, KGF, EGF and IGF-1 are overexpressed in CRPC and can stimulate AR transcription in the absence of ligand
• The MAPK and PI3K/AKT pathways are probably the leading pathways, which regulate the phosphorylation of AR
coactivators, such as SRC-1 and TIF2, or the AR protein itself
Sadar MD. J. Biol. Chem. 1999;
CRPC: Teoria adattativa
• The ability of CRPC to convert adrenal androgens into T and DHT by
expressing or up-regulating
steroidogenic enzymes including
CYP17A1, HSD3B1, HSD17B3, CYP19A1, or UGT2B17
• CRPC cells were also capable of
synthetising de novo androgens from membranes’ cholesterol molecules.
Montgomery RB, Cancer Res. 2008;
CRPC: Teoria adattativa
• AR splice variants with truncated LBD, which have the potential to be
constitutively active regardless of the presence of androgen
Sun S, J. Clin. Invest. 2010;
CRPC: Stato dell’arte
• Enzalutamide
• Abiraterone
• (Apalutamide)
AR Splice Variants (ARv)
• ADT induces constitutively active splice variants which drive development of CRPC
• ARv567 (43%) and ARv7 (24%) are the most prevalent:
‒ Both lack ligand-binding domain
‒ AR-V7 also lacks Hinge domain
• Inhibition of ARv7 transcription by FOXO1 (potent AR suppressor)
• May contribute to resistance to ENZA & ABI
• Taxanes inhibit nuclear translocation of ARv567, not ARv7
ABI, abiraterone; ADT, androgen deprivation therapy; AR, androgen receptor; ARV, AR splice variant; CRPC, castration-resistant prostate cancer;
ENZA, enzalutamide; FOXO1, forkhead box protein O1
Guo Z, et al. Int J Biol Sci. 2011; Lu C & Luo J. Transl Androl Urol. 2013; Sun S, et al. J Clin Invest. 2010; Mediwala SN, et al. Prostate. 2013; Bohrer LR, et al. Prostate.
2013;Li Y. Cancer Res. 2013; Mostaghel EA, et al. Clin Cancer Res. 2011; Thadani-Mulero M, et al. Cancer Res. 2014.
AR-FL AR-45 AR-V7 AR-V1 AR-V4 AR-V3 AR-V567
AR-FL: Full-Length Androgen Receptor NTD: N-Terminal Domain
DBD: DNA-Binding Domain LBD: Ligand-Binding Domain
U: Unique N- or C-terminal sequence
AR-V7 e Resistenza ad Enzalutamide & Abiraterone
A total of 31 enzalutamide-treated patients and 31 abiraterone-treated patients were enrolled, of whom 39% and 19%, respectively, had detectable AR-V7 in circulating tumor cells
AR-V7, androgen receptor splice variant 7; PSA, prostate-specific antigen Antonarakis ES, et al. N Engl J Med. 2014.
Abiraterone-treated patients Enzalutamide-treated patients
EPI 002 (antagonista AR AF-1): dati preclinici
Genes distinctively regulated by AR-V7:
Expression of these genes was not induced by androgens
EPI significantly reduced the level of expression of UBE2C, CDC20 and AKT1
EPI blocks the non-canonical transcriptional program regulated by constitutively active AR-splice variant
Yang YC et al. Clin Cancer Res 2016
UBE2C CDC20 AKT1
CRPC: sequenziamento “clinico”
Robinson D et al. Cell. 2015
Robinson D, et al. Cell. 2015.
mCRPC: Alterazioni genomiche
71%
21% RB loss 9% CCND1
23%
49%
23%
62.7%
53.3%
40.7%
56.7%
13.3%
7.3%
AR TP53 PTEN ETS fusions BRCA2 ATM
AR, androgen receptor; ATM, ataxia-telangiectasia mutated; BRCA, BReast CAncer susceptibility gene; CCND1, cyclin D1; ETS, E26 transformation-specific transcription factor; mCRPC, metastatic castration-resistant prostate cancer; PTEN, phosphatase and tensin homolog; RB, retinoblastoma; TP53, tumor protein p53
Multipli modelli di diffusione metastatica
Gundem G et al. Nature. 2015
La “Lineage Plasticity” Conferisce Resistenza alle terapie AR-targeted
Mu P, et al. Science. 2017; Francis JC, et al. Oncotarget. 2018.
A phenotype shift from
AR-dependent luminal cells to
AR-independent basal-like cells
Tp53
RB1
PTEN
EZH2 SOX2
ANDROGEN INDIFFERENCE
Ku, SY et al. Science. 2017; Mu P et al. Science. 2017.
La Perdita di espressione di Tp53/RB1 (e PTEN) promuove la “Lineage Plasticity” e l’ “Androgeno- indipendenza”
PTEN, phosphatase and tensin homolog; RB, retinoblastoma
• SOX2 promotes lineage plasticity in TP53- and RB1-deficient PCa
• SOX9 promotes lineage plasticity,
invasion, cell fate, cytoskeletal
alterations and EMT in mice with
PTEN-loss PCa
SOX2 Promuove la “Lineage Plasticity” e la
resitenza ad AR in cellule prostatiche con Perdita di espressione di TP53- and RB1
Mu P, et al. Science. 2017.
Abi, abiraterone; Adeno, adenocarcinoma; AR, androgen receptor; CRPC, castration-resistant prostate cancer; EMT, epithelial-mesenchymal-transition; Enz, enzalutamide;
GAPDH, glyceraldehyde 3-phosphate dehydrogenase; NE, neuroendocrine; PCa, prostate cancer; PTEN, phosphatase and tensin homolog; RB1, retinoblastoma 1;
SOX2, SRY Box 2; TP53, tumor protein p53
L’inibizione di Ezh2 ripristina la sensibilità a enzalutamide
Sheng YK et al. Science. 2017.
Conclusioni
• La fase CRPC rappresenta tutt’oggi una sfida importante nella gestione della neoplasia prostatica
• La selezione clonale e la capacità adattativa dei cloni cellulari neoplastici coesistono
• Il sequenziamento genico ha permesso di identificare le vie del segnale
prevalentemente responsabili della proliferazione neoplastica nella fase CRPC
• La metastatizzazione non è solo un percorso lineare a partire dal tumore primitivo ma alterazioni all’interno dei siti metastatici caratterizzano
differenti subcloni neoplastici
• La «lineage plasticity» è un meccanismo di resistenza ai trattamenti ormonali ma l’identificazione e quindi l’inibizione dei fattori responsabili di tale
processo possono rappresentare un nuovo bersaglio terapeutico.
Conclusioni
Cattrini C, Zanardi E, and Boccardo F.
Crit Rev Oncol Hematol. 2017.
